1 /*
   2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.util;






  27 
  28 /**
  29  * This class provides a skeletal implementation of the {@link List}
  30  * interface to minimize the effort required to implement this interface
  31  * backed by a "random access" data store (such as an array).  For sequential
  32  * access data (such as a linked list), {@link AbstractSequentialList} should
  33  * be used in preference to this class.
  34  *
  35  * <p>To implement an unmodifiable list, the programmer needs only to extend
  36  * this class and provide implementations for the {@link #get(int)} and
  37  * {@link List#size() size()} methods.
  38  *
  39  * <p>To implement a modifiable list, the programmer must additionally
  40  * override the {@link #set(int, Object) set(int, E)} method (which otherwise
  41  * throws an {@code UnsupportedOperationException}).  If the list is
  42  * variable-size the programmer must additionally override the
  43  * {@link #add(int, Object) add(int, E)} and {@link #remove(int)} methods.
  44  *
  45  * <p>The programmer should generally provide a void (no argument) and collection
  46  * constructor, as per the recommendation in the {@link Collection} interface
  47  * specification.
  48  *
  49  * <p>Unlike the other abstract collection implementations, the programmer does
  50  * <i>not</i> have to provide an iterator implementation; the iterator and
  51  * list iterator are implemented by this class, on top of the "random access"
  52  * methods:
  53  * {@link #get(int)},
  54  * {@link #set(int, Object) set(int, E)},
  55  * {@link #add(int, Object) add(int, E)} and
  56  * {@link #remove(int)}.
  57  *
  58  * <p>The documentation for each non-abstract method in this class describes its
  59  * implementation in detail.  Each of these methods may be overridden if the
  60  * collection being implemented admits a more efficient implementation.
  61  *
  62  * <p>This class is a member of the
  63  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
  64  * Java Collections Framework</a>.
  65  *
  66  * @author  Josh Bloch
  67  * @author  Neal Gafter
  68  * @since 1.2
  69  */
  70 
  71 public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> {
  72     /**
  73      * Sole constructor.  (For invocation by subclass constructors, typically
  74      * implicit.)
  75      */
  76     protected AbstractList() {
  77     }
  78 
  79     /**
  80      * Appends the specified element to the end of this list (optional
  81      * operation).
  82      *
  83      * <p>Lists that support this operation may place limitations on what
  84      * elements may be added to this list.  In particular, some
  85      * lists will refuse to add null elements, and others will impose
  86      * restrictions on the type of elements that may be added.  List
  87      * classes should clearly specify in their documentation any restrictions
  88      * on what elements may be added.
  89      *
  90      * @implSpec
  91      * This implementation calls {@code add(size(), e)}.
  92      *
  93      * <p>Note that this implementation throws an
  94      * {@code UnsupportedOperationException} unless
  95      * {@link #add(int, Object) add(int, E)} is overridden.
  96      *
  97      * @param e element to be appended to this list
  98      * @return {@code true} (as specified by {@link Collection#add})
  99      * @throws UnsupportedOperationException if the {@code add} operation
 100      *         is not supported by this list
 101      * @throws ClassCastException if the class of the specified element
 102      *         prevents it from being added to this list
 103      * @throws NullPointerException if the specified element is null and this
 104      *         list does not permit null elements
 105      * @throws IllegalArgumentException if some property of this element
 106      *         prevents it from being added to this list
 107      */
 108     public boolean add(E e) {
 109         add(size(), e);
 110         return true;
 111     }
 112 
 113     /**
 114      * {@inheritDoc}
 115      *
 116      * @throws IndexOutOfBoundsException {@inheritDoc}
 117      */
 118     abstract public E get(int index);
 119 
 120     /**
 121      * {@inheritDoc}
 122      *
 123      * @implSpec
 124      * This implementation always throws an
 125      * {@code UnsupportedOperationException}.
 126      *
 127      * @throws UnsupportedOperationException {@inheritDoc}
 128      * @throws ClassCastException            {@inheritDoc}
 129      * @throws NullPointerException          {@inheritDoc}
 130      * @throws IllegalArgumentException      {@inheritDoc}
 131      * @throws IndexOutOfBoundsException     {@inheritDoc}
 132      */
 133     public E set(int index, E element) {
 134         throw new UnsupportedOperationException();
 135     }
 136 
 137     /**
 138      * {@inheritDoc}
 139      *
 140      * @implSpec
 141      * This implementation always throws an
 142      * {@code UnsupportedOperationException}.
 143      *
 144      * @throws UnsupportedOperationException {@inheritDoc}
 145      * @throws ClassCastException            {@inheritDoc}
 146      * @throws NullPointerException          {@inheritDoc}
 147      * @throws IllegalArgumentException      {@inheritDoc}
 148      * @throws IndexOutOfBoundsException     {@inheritDoc}
 149      */
 150     public void add(int index, E element) {
 151         throw new UnsupportedOperationException();
 152     }
 153 
 154     /**
 155      * {@inheritDoc}
 156      *
 157      * @implSpec
 158      * This implementation always throws an
 159      * {@code UnsupportedOperationException}.
 160      *
 161      * @throws UnsupportedOperationException {@inheritDoc}
 162      * @throws IndexOutOfBoundsException     {@inheritDoc}
 163      */
 164     public E remove(int index) {
 165         throw new UnsupportedOperationException();
 166     }
 167 
 168 
 169     // Search Operations
 170 
 171     /**
 172      * {@inheritDoc}
 173      *
 174      * @implSpec
 175      * This implementation first gets a list iterator (with
 176      * {@code listIterator()}).  Then, it iterates over the list until the
 177      * specified element is found or the end of the list is reached.
 178      *
 179      * @throws ClassCastException   {@inheritDoc}
 180      * @throws NullPointerException {@inheritDoc}
 181      */
 182     public int indexOf(Object o) {












 183         ListIterator<E> it = listIterator();
 184         if (o==null) {
 185             while (it.hasNext())
 186                 if (it.next()==null)
 187                     return it.previousIndex();
 188         } else {
 189             while (it.hasNext())
 190                 if (o.equals(it.next()))
 191                     return it.previousIndex();
 192         }
 193         return -1;
 194     }

 195 
 196     /**
 197      * {@inheritDoc}
 198      *
 199      * @implSpec
 200      * This implementation first gets a list iterator that points to the end
 201      * of the list (with {@code listIterator(size())}).  Then, it iterates
 202      * backwards over the list until the specified element is found, or the
 203      * beginning of the list is reached.
 204      *
 205      * @throws ClassCastException   {@inheritDoc}
 206      * @throws NullPointerException {@inheritDoc}
 207      */
 208     public int lastIndexOf(Object o) {




 209         ListIterator<E> it = listIterator(size());
 210         if (o==null) {
 211             while (it.hasPrevious())
 212                 if (it.previous()==null)








 213                     return it.nextIndex();
 214         } else {
 215             while (it.hasPrevious())
 216                 if (o.equals(it.previous()))
 217                     return it.nextIndex();
 218         }
 219         return -1;
 220     }

 221 
 222 
 223     // Bulk Operations
 224 
 225     /**
 226      * Removes all of the elements from this list (optional operation).
 227      * The list will be empty after this call returns.
 228      *
 229      * @implSpec
 230      * This implementation calls {@code removeRange(0, size())}.
 231      *
 232      * <p>Note that this implementation throws an
 233      * {@code UnsupportedOperationException} unless {@code remove(int
 234      * index)} or {@code removeRange(int fromIndex, int toIndex)} is
 235      * overridden.
 236      *
 237      * @throws UnsupportedOperationException if the {@code clear} operation
 238      *         is not supported by this list
 239      */
 240     public void clear() {
 241         removeRange(0, size());
 242     }
 243 
 244     /**
 245      * {@inheritDoc}
 246      *
 247      * @implSpec
 248      * This implementation gets an iterator over the specified collection
 249      * and iterates over it, inserting the elements obtained from the
 250      * iterator into this list at the appropriate position, one at a time,
 251      * using {@code add(int, E)}.
 252      * Many implementations will override this method for efficiency.
 253      *
 254      * <p>Note that this implementation throws an
 255      * {@code UnsupportedOperationException} unless
 256      * {@link #add(int, Object) add(int, E)} is overridden.
 257      *
 258      * @throws UnsupportedOperationException {@inheritDoc}
 259      * @throws ClassCastException            {@inheritDoc}
 260      * @throws NullPointerException          {@inheritDoc}
 261      * @throws IllegalArgumentException      {@inheritDoc}
 262      * @throws IndexOutOfBoundsException     {@inheritDoc}
 263      */
 264     public boolean addAll(int index, Collection<? extends E> c) {
 265         rangeCheckForAdd(index);
 266         boolean modified = false;
 267         for (E e : c) {


 268             add(index++, e);
 269             modified = true;
 270         }
 271         return modified;
 272     }
 273 
 274 
 275     // Iterators
 276 
 277     /**
 278      * Returns an iterator over the elements in this list in proper sequence.
 279      *
 280      * @implSpec
 281      * This implementation returns a straightforward implementation of the
 282      * iterator interface, relying on the backing list's {@code size()},
 283      * {@code get(int)}, and {@code remove(int)} methods.
 284      *
 285      * <p>Note that the iterator returned by this method will throw an
 286      * {@link UnsupportedOperationException} in response to its
 287      * {@code remove} method unless the list's {@code remove(int)} method is
 288      * overridden.
 289      *
 290      * <p>This implementation can be made to throw runtime exceptions in the
 291      * face of concurrent modification, as described in the specification
 292      * for the (protected) {@link #modCount} field.
 293      *
 294      * @return an iterator over the elements in this list in proper sequence
 295      */
 296     public Iterator<E> iterator() {
 297         return new Itr();
 298     }
 299 
 300     /**
 301      * {@inheritDoc}
 302      *
 303      * @implSpec
 304      * This implementation returns {@code listIterator(0)}.
 305      *
 306      * @see #listIterator(int)
 307      */
 308     public ListIterator<E> listIterator() {
 309         return listIterator(0);
 310     }
 311 
 312     /**
 313      * {@inheritDoc}
 314      *
 315      * @implSpec
 316      * This implementation returns a straightforward implementation of the
 317      * {@code ListIterator} interface that extends the implementation of the
 318      * {@code Iterator} interface returned by the {@code iterator()} method.
 319      * The {@code ListIterator} implementation relies on the backing list's
 320      * {@code get(int)}, {@code set(int, E)}, {@code add(int, E)}
 321      * and {@code remove(int)} methods.
 322      *
 323      * <p>Note that the list iterator returned by this implementation will
 324      * throw an {@link UnsupportedOperationException} in response to its
 325      * {@code remove}, {@code set} and {@code add} methods unless the
 326      * list's {@code remove(int)}, {@code set(int, E)}, and
 327      * {@code add(int, E)} methods are overridden.
 328      *
 329      * <p>This implementation can be made to throw runtime exceptions in the
 330      * face of concurrent modification, as described in the specification for
 331      * the (protected) {@link #modCount} field.
 332      *
 333      * @throws IndexOutOfBoundsException {@inheritDoc}
 334      */
 335     public ListIterator<E> listIterator(final int index) {
 336         rangeCheckForAdd(index);
 337 
 338         return new ListItr(index);
 339     }
 340 
 341     private class Itr implements Iterator<E> {
 342         /**
 343          * Index of element to be returned by subsequent call to next.
 344          */
 345         int cursor = 0;
 346 
 347         /**
 348          * Index of element returned by most recent call to next or
 349          * previous.  Reset to -1 if this element is deleted by a call
 350          * to remove.
 351          */
 352         int lastRet = -1;
 353 
 354         /**
 355          * The modCount value that the iterator believes that the backing
 356          * List should have.  If this expectation is violated, the iterator
 357          * has detected concurrent modification.
 358          */
 359         int expectedModCount = modCount;
 360 
 361         public boolean hasNext() {
 362             return cursor != size();
 363         }
 364 
 365         public E next() {
 366             checkForComodification();
 367             try {
 368                 int i = cursor;
 369                 E next = get(i);
 370                 lastRet = i;
 371                 cursor = i + 1;
 372                 return next;
 373             } catch (IndexOutOfBoundsException e) {
 374                 checkForComodification();
 375                 throw new NoSuchElementException();
 376             }
 377         }
 378 
 379         public void remove() {
 380             if (lastRet < 0)
 381                 throw new IllegalStateException();
 382             checkForComodification();
 383 
 384             try {
 385                 AbstractList.this.remove(lastRet);
 386                 if (lastRet < cursor)
 387                     cursor--;
 388                 lastRet = -1;
 389                 expectedModCount = modCount;
 390             } catch (IndexOutOfBoundsException e) {
 391                 throw new ConcurrentModificationException();
 392             }
 393         }
 394 
 395         final void checkForComodification() {
 396             if (modCount != expectedModCount)
 397                 throw new ConcurrentModificationException();
 398         }
 399     }
 400 
 401     private class ListItr extends Itr implements ListIterator<E> {
 402         ListItr(int index) {
 403             cursor = index;
 404         }
 405 
 406         public boolean hasPrevious() {
 407             return cursor != 0;
 408         }
 409 
 410         public E previous() {
 411             checkForComodification();
 412             try {
 413                 int i = cursor - 1;
 414                 E previous = get(i);
 415                 lastRet = cursor = i;
 416                 return previous;
 417             } catch (IndexOutOfBoundsException e) {
 418                 checkForComodification();
 419                 throw new NoSuchElementException();
 420             }
 421         }
 422 
 423         public int nextIndex() {
 424             return cursor;
 425         }
 426 
 427         public int previousIndex() {
 428             return cursor-1;
 429         }
 430 
 431         public void set(E e) {
 432             if (lastRet < 0)
 433                 throw new IllegalStateException();
 434             checkForComodification();
 435 
 436             try {
 437                 AbstractList.this.set(lastRet, e);
 438                 expectedModCount = modCount;
 439             } catch (IndexOutOfBoundsException ex) {
 440                 throw new ConcurrentModificationException();
 441             }
 442         }
 443 
 444         public void add(E e) {
 445             checkForComodification();
 446 
 447             try {
 448                 int i = cursor;
 449                 AbstractList.this.add(i, e);
 450                 lastRet = -1;
 451                 cursor = i + 1;
 452                 expectedModCount = modCount;
 453             } catch (IndexOutOfBoundsException ex) {
 454                 throw new ConcurrentModificationException();
 455             }
 456         }
 457     }
 458 
 459     /**
 460      * {@inheritDoc}
 461      *
 462      * @implSpec
 463      * This implementation returns a list that subclasses
 464      * {@code AbstractList}.  The subclass stores, in private fields, the
 465      * offset of the subList within the backing list, the size of the subList
 466      * (which can change over its lifetime), and the expected
 467      * {@code modCount} value of the backing list.  There are two variants
 468      * of the subclass, one of which implements {@code RandomAccess}.
 469      * If this list implements {@code RandomAccess} the returned list will
 470      * be an instance of the subclass that implements {@code RandomAccess}.
 471      *
 472      * <p>The subclass's {@code set(int, E)}, {@code get(int)},
 473      * {@code add(int, E)}, {@code remove(int)}, {@code addAll(int,
 474      * Collection)} and {@code removeRange(int, int)} methods all
 475      * delegate to the corresponding methods on the backing abstract list,
 476      * after bounds-checking the index and adjusting for the offset.  The
 477      * {@code addAll(Collection c)} method merely returns {@code addAll(size,
 478      * c)}.
 479      *
 480      * <p>The {@code listIterator(int)} method returns a "wrapper object"
 481      * over a list iterator on the backing list, which is created with the
 482      * corresponding method on the backing list.  The {@code iterator} method
 483      * merely returns {@code listIterator()}, and the {@code size} method
 484      * merely returns the subclass's {@code size} field.
 485      *
 486      * <p>All methods first check to see if the actual {@code modCount} of
 487      * the backing list is equal to its expected value, and throw a
 488      * {@code ConcurrentModificationException} if it is not.
 489      *
 490      * @throws IndexOutOfBoundsException if an endpoint index value is out of range
 491      *         {@code (fromIndex < 0 || toIndex > size)}
 492      * @throws IllegalArgumentException if the endpoint indices are out of order
 493      *         {@code (fromIndex > toIndex)}
 494      */
 495     public List<E> subList(int fromIndex, int toIndex) {
 496         return (this instanceof RandomAccess ?
 497                 new RandomAccessSubList<>(this, fromIndex, toIndex) :
 498                 new SubList<>(this, fromIndex, toIndex));
 499     }
 500 
 501     // Comparison and hashing
 502 
 503     /**
 504      * Compares the specified object with this list for equality.  Returns
 505      * {@code true} if and only if the specified object is also a list, both
 506      * lists have the same size, and all corresponding pairs of elements in
 507      * the two lists are <i>equal</i>.  (Two elements {@code e1} and
 508      * {@code e2} are <i>equal</i> if {@code (e1==null ? e2==null :
 509      * e1.equals(e2))}.)  In other words, two lists are defined to be
 510      * equal if they contain the same elements in the same order.
 511      *
 512      * @implSpec
 513      * This implementation first checks if the specified object is this
 514      * list. If so, it returns {@code true}; if not, it checks if the
 515      * specified object is a list. If not, it returns {@code false}; if so,
 516      * it iterates over both lists, comparing corresponding pairs of elements.
 517      * If any comparison returns {@code false}, this method returns
 518      * {@code false}.  If either iterator runs out of elements before the
 519      * other it returns {@code false} (as the lists are of unequal length);
 520      * otherwise it returns {@code true} when the iterations complete.
 521      *
 522      * @param o the object to be compared for equality with this list
 523      * @return {@code true} if the specified object is equal to this list
 524      */

 525     public boolean equals(Object o) {
 526         if (o == this)
 527             return true;
 528         if (!(o instanceof List))
 529             return false;
 530 
 531         ListIterator<E> e1 = listIterator();
 532         ListIterator<?> e2 = ((List<?>) o).listIterator();
 533         while (e1.hasNext() && e2.hasNext()) {
 534             E o1 = e1.next();
 535             Object o2 = e2.next();
 536             if (!(o1==null ? o2==null : o1.equals(o2)))
 537                 return false;
 538         }
 539         return !(e1.hasNext() || e2.hasNext());
 540     }
 541 
 542     /**
 543      * Returns the hash code value for this list.
 544      *
 545      * @implSpec
 546      * This implementation uses exactly the code that is used to define the
 547      * list hash function in the documentation for the {@link List#hashCode}
 548      * method.
 549      *
 550      * @return the hash code value for this list
 551      */
 552     public int hashCode() {
 553         int hashCode = 1;
 554         for (E e : this)
 555             hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());



 556         return hashCode;
 557     }
 558 
 559     /**
 560      * Removes from this list all of the elements whose index is between
 561      * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
 562      * Shifts any succeeding elements to the left (reduces their index).
 563      * This call shortens the list by {@code (toIndex - fromIndex)} elements.
 564      * (If {@code toIndex==fromIndex}, this operation has no effect.)
 565      *
 566      * <p>This method is called by the {@code clear} operation on this list
 567      * and its subLists.  Overriding this method to take advantage of
 568      * the internals of the list implementation can <i>substantially</i>
 569      * improve the performance of the {@code clear} operation on this list
 570      * and its subLists.
 571      *
 572      * @implSpec
 573      * This implementation gets a list iterator positioned before
 574      * {@code fromIndex}, and repeatedly calls {@code ListIterator.next}
 575      * followed by {@code ListIterator.remove} until the entire range has
 576      * been removed.  <b>Note: if {@code ListIterator.remove} requires linear
 577      * time, this implementation requires quadratic time.</b>
 578      *
 579      * @param fromIndex index of first element to be removed
 580      * @param toIndex index after last element to be removed
 581      */
 582     protected void removeRange(int fromIndex, int toIndex) {
 583         ListIterator<E> it = listIterator(fromIndex);
 584         for (int i=0, n=toIndex-fromIndex; i<n; i++) {
 585             it.next();
 586             it.remove();
 587         }
 588     }
 589 
 590     /**
 591      * The number of times this list has been <i>structurally modified</i>.
 592      * Structural modifications are those that change the size of the
 593      * list, or otherwise perturb it in such a fashion that iterations in
 594      * progress may yield incorrect results.
 595      *
 596      * <p>This field is used by the iterator and list iterator implementation
 597      * returned by the {@code iterator} and {@code listIterator} methods.
 598      * If the value of this field changes unexpectedly, the iterator (or list
 599      * iterator) will throw a {@code ConcurrentModificationException} in
 600      * response to the {@code next}, {@code remove}, {@code previous},
 601      * {@code set} or {@code add} operations.  This provides
 602      * <i>fail-fast</i> behavior, rather than non-deterministic behavior in
 603      * the face of concurrent modification during iteration.
 604      *
 605      * <p><b>Use of this field by subclasses is optional.</b> If a subclass
 606      * wishes to provide fail-fast iterators (and list iterators), then it
 607      * merely has to increment this field in its {@code add(int, E)} and
 608      * {@code remove(int)} methods (and any other methods that it overrides
 609      * that result in structural modifications to the list).  A single call to
 610      * {@code add(int, E)} or {@code remove(int)} must add no more than
 611      * one to this field, or the iterators (and list iterators) will throw
 612      * bogus {@code ConcurrentModificationExceptions}.  If an implementation
 613      * does not wish to provide fail-fast iterators, this field may be
 614      * ignored.
 615      */
 616     protected transient int modCount = 0;
 617 
 618     private void rangeCheckForAdd(int index) {
 619         if (index < 0 || index > size())
 620             throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 621     }
 622 
 623     private String outOfBoundsMsg(int index) {
 624         return "Index: "+index+", Size: "+size();
 625     }
 626 }
 627 
 628 class SubList<E> extends AbstractList<E> {
 629     private final AbstractList<E> l;
 630     private final int offset;
 631     private int size;
 632 
 633     SubList(AbstractList<E> list, int fromIndex, int toIndex) {
 634         if (fromIndex < 0)
 635             throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
 636         if (toIndex > list.size())
 637             throw new IndexOutOfBoundsException("toIndex = " + toIndex);
 638         if (fromIndex > toIndex)
 639             throw new IllegalArgumentException("fromIndex(" + fromIndex +
 640                                                ") > toIndex(" + toIndex + ")");
 641         l = list;
 642         offset = fromIndex;
 643         size = toIndex - fromIndex;
 644         this.modCount = l.modCount;
 645     }
 646 
 647     public E set(int index, E element) {
 648         rangeCheck(index);
 649         checkForComodification();
 650         return l.set(index+offset, element);
 651     }
 652 
 653     public E get(int index) {
 654         rangeCheck(index);
 655         checkForComodification();
 656         return l.get(index+offset);
 657     }
 658 
 659     public int size() {
 660         checkForComodification();
 661         return size;
 662     }
 663 
 664     public void add(int index, E element) {
 665         rangeCheckForAdd(index);
 666         checkForComodification();
 667         l.add(index+offset, element);
 668         this.modCount = l.modCount;
 669         size++;
 670     }
 671 
 672     public E remove(int index) {
 673         rangeCheck(index);
 674         checkForComodification();
 675         E result = l.remove(index+offset);
 676         this.modCount = l.modCount;
 677         size--;
 678         return result;
 679     }
 680 
 681     protected void removeRange(int fromIndex, int toIndex) {
 682         checkForComodification();
 683         l.removeRange(fromIndex+offset, toIndex+offset);
 684         this.modCount = l.modCount;
 685         size -= (toIndex-fromIndex);
 686     }
 687 
 688     public boolean addAll(Collection<? extends E> c) {
 689         return addAll(size, c);
 690     }
 691 
 692     public boolean addAll(int index, Collection<? extends E> c) {
 693         rangeCheckForAdd(index);
 694         int cSize = c.size();
 695         if (cSize==0)
 696             return false;
 697 
 698         checkForComodification();
 699         l.addAll(offset+index, c);
 700         this.modCount = l.modCount;
 701         size += cSize;
 702         return true;
 703     }
 704 
 705     public Iterator<E> iterator() {
 706         return listIterator();
 707     }
 708 
 709     public ListIterator<E> listIterator(final int index) {
 710         checkForComodification();
 711         rangeCheckForAdd(index);
 712 
 713         return new ListIterator<E>() {
 714             private final ListIterator<E> i = l.listIterator(index+offset);
 715 
 716             public boolean hasNext() {
 717                 return nextIndex() < size;
 718             }
 719 
 720             public E next() {
 721                 if (hasNext())
 722                     return i.next();
 723                 else
 724                     throw new NoSuchElementException();
 725             }
 726 
 727             public boolean hasPrevious() {
 728                 return previousIndex() >= 0;
 729             }
 730 
 731             public E previous() {
 732                 if (hasPrevious())
 733                     return i.previous();
 734                 else
 735                     throw new NoSuchElementException();
 736             }
 737 
 738             public int nextIndex() {
 739                 return i.nextIndex() - offset;
 740             }
 741 
 742             public int previousIndex() {
 743                 return i.previousIndex() - offset;
 744             }
 745 
 746             public void remove() {
 747                 i.remove();
 748                 SubList.this.modCount = l.modCount;
 749                 size--;
 750             }
 751 
 752             public void set(E e) {
 753                 i.set(e);
 754             }
 755 
 756             public void add(E e) {
 757                 i.add(e);
 758                 SubList.this.modCount = l.modCount;
 759                 size++;
 760             }
 761         };
 762     }
 763 
 764     public List<E> subList(int fromIndex, int toIndex) {
 765         return new SubList<>(this, fromIndex, toIndex);
 766     }
 767 
 768     private void rangeCheck(int index) {
 769         if (index < 0 || index >= size)
 770             throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 771     }
 772 
 773     private void rangeCheckForAdd(int index) {
 774         if (index < 0 || index > size)
 775             throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 776     }
 777 
 778     private String outOfBoundsMsg(int index) {
 779         return "Index: "+index+", Size: "+size;
 780     }
 781 
 782     private void checkForComodification() {
 783         if (this.modCount != l.modCount)
 784             throw new ConcurrentModificationException();
 785     }
 786 }
 787 
 788 class RandomAccessSubList<E> extends SubList<E> implements RandomAccess {
 789     RandomAccessSubList(AbstractList<E> list, int fromIndex, int toIndex) {
 790         super(list, fromIndex, toIndex);
 791     }
 792 
 793     public List<E> subList(int fromIndex, int toIndex) {
 794         return new RandomAccessSubList<>(this, fromIndex, toIndex);
 795     }
 796 }
--- EOF ---